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Slaughter, Daniel Stephen, and d. slaughter@aip org au. "Superelastic Electron Scattering from Caesium." Flinders University. Chemistry Physics and Earth Sciences, 2007. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20071009.100421.
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This thesis describes an experimental study of superelastic electron scattering from
the 6^2P_3/2
state of caesium. The present status of electron-atom collision studies is
initially reviewed and the motivation behind the current work is then presented. A
description of the theoretical framework is subsequently provided in the context of
the present experimental study, followed by an overview of the several theoretical
approaches for describing electron-atom interactions which are currently available.
The apparatus and experimental setup used throughout the project are also described
in detail. Technical specifications and data are provided, including diagrams (where
appropriate) for a laser frequency locking system, electron gun and spectrometer,
atomic beam source and data acquisition system. The experimental procedures are
explained and discussed, including a detailed analysis of the optical pumping
process required to excite the atomic target. A substantial component of this project
was to address several potential sources of systematic error and to reduce these
wherever possible. All of the errors and uncertainties relevant to the experiment are
discussed in chapter 5.
In chapter 6 the results of the present superelastic electron scattering experiments are
reported for incident electron energies of 5.5eV, 8.5eV and 13.5eV, corresponding
to superelastic electron energies of 7eV, 10eV and 15eV. These results are presented
as three reduced Stokes parameters, P1, P2, P3 and a coherence parameter, P+ . For
comparison, predictions from a number of currently available theories are presented alongside the experimental results. Finally, conclusions are drawn on this work in the context of the current status of electron-atom scattering from alkali-metals.
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Alarcon, Tarquino Eduardo Augusto. "Structural fatigue of superelastic NiTi wires." Thesis, Brest, 2018. http://www.theses.fr/2018BRES0019/document.
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Ce travail de thèse aborde les conditions et les mécanismes qui conduisent des fils superélastiques de NiTi à la rupture sous chargement mécanique cyclique. Les alliages à mémoire de forme du type NiTi présentent des propriétés thermomécaniques fonctionnelles comme la superélasticité et l’effet de mémoire de forme simple et double, lesquels sont générées grâce aux transformations de phase martensitiques provoquées soit par un changement de la contrainte ou de la température. Ces transformations de phase sont en principe des processus totalement réversibles et sans endommagement. Cependant, lorsque le NiTi est soumis à des transformations de phase induites par des contraintes cycliques, la performance en fatigue de l’alliage chute considérablement par rapport au NiTi non-transformant. La plupart des courbes S-N de fatigue rapportant cette chute ont été mesurées sur des fils NiTi a section constante dans lesquels les transformations martensitiques se développent de façon hétérogene par nucléation et propagation de bandes de cisaillement. De plus, d'après notre expérience, des essais de fatigue sur des échantillons de fils à section constante entrainent la rupture à l'intérieur des mors de la machine d'essai. Par conséquent, les valeurs de contrainte-déformation rapportées dans les courbes S-N ne sont pas nécessairement représentatives des conditions mécaniques critiques qui conduisent le matériau à la rupture. Dans le but de mieux caractériser les performances en fatigue des fils NiTi, nous avons effectué une série de tests de fatigue en traction-traction, tout en utilisant des échantillons sous forme ≪ diabolo ≫. La géométrie de ces échantillons nous a permis de confiner tous les processus de transformation martensitique et de fatigue dans un volume utile bien défini. La caractérisation du comportement thermomécanique de ces échantillons a été réalisée en combinant plusieurs techniques expérimentales et d'analyse telles que la corrélation d'image numérique(DIC), la thermographie infrarouge, la diffraction des rayons X à source synchrotron, la microscopie optique, la microscopie électronique à balayage et l'analyse par éléments finis. Une attention particulière à été portée à la performance de NiTi dans le régime à grand nombre de cycles (HCF) dans laquelle le matériau présente un comportement élastique ou une transformation de phase intermédiaire (appelée R-phase). Les résultats des tests de fatigue nous ont permis de distinguer les étapes de nucléation et de propagation des fissures pendant la durée de vie totale de nos échantillons. Afin de mieux comprendre les mécanismes qui conduisent à la nucléation des fissures, nous avons appliqué la méthode de l’auto-échauffement, qui a démontré son efficacité dans la prédiction de fatigue dans les cas des alliages d'aluminium et des alliages d'acier. Cette méthode corrèle l'élévation de température d'un échantillon soumis à différentes amplitudes de charge cyclique avec des mécanismes de dissipation d'énergie. Ces mécanismes dissipatifs sont après associés à l’accumulation d’endommagement locale dans le matériau. La méthode d'autoéchauffement a été réalisée en utilisant des mesures de champs thermiques des d'échantillons de NiTi sous forme diabolo pendant de chargement cycliqueThis Ph.D. dissertation thesis addresses the conditions and mechanisms that lead superelastic NiTi wires to fail under cyclic mechanical loads. NiTi shape memory alloys exhibit functional thermomechanical properties (superelasticity, shape memory effect, thermal actuation) due to martensitic phase transformations caused by a change of the applied stress and temperature. These phase transformations are though as fully reversible damage-free processes, however, when NiTi is subjected to repetitive stress-induced phase transformations its fatigue performance drops drastically in comparison to non-transforming NiTi. Most of fatigue S-N curves reporting this drop were measured on straight NiTi wires in which martensitic transformations proceed heterogeneously through nucleation and propagation of shear bands. Moreover, from our experience fatigue testing straight wire samples results in undesired failure inside the testing machine clamps. Hence, the reported stress-strain values in S-N curves are not necessarily representative of the critical mechanical conditions that lead the material to failure. With the aim of better characterize the fatigue performance of NiTi wires, we started by carrying out a series of pull-pull fatigue tests using hourglass-shaped samples. This sample geometry allowed us to confine all martensitic transformation and related material fatigue processes into a well-defined gauge volume. The samples’ characterization was performed by combining several experimental and analysis techniques such as Digital Image Correlation, Infrared Thermography, Synchrotron-source X-ray diffraction, Optical Microscopy, Scanning Electron Microscopy and Finite Element Analysis. A special attention was paid to the High Cycle Fatigue (HCF) performance of NiTi in which the material shows elastic behavior and/or an intermediate phase transformation (so-called R-phase). The results from HCF tests allowed us to distinguish crack nucleation and crack propagation stages during the total life of our NiTi samples. In order to get a better understanding of the mechanisms that lead to crack nucleation, we applied the nonconventional Self-Heating fatigue assessment method, which has shown efficiency in the case of aluminum and steel alloys. This method correlates the temperature elevation of a sample subjected to different cyclic load amplitudes with energy dissipating mechanisms that contribute to accumulating local damage in the material. The Self-Heating method was performed using full-field thermal measurements of cyclically loaded NiTi hourglass-shaped samples
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Joris, Oliver Pieter Johnathan. "Diffraction experiments on superelastic beta titanium alloys." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/43967.
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This thesis investigates superelasticity in metastable beta titanium alloys that contain substantial additions of Mo, principally. Superelasticity arises from a reversible transformation from the β to the orthorhombic alpha double prime (α") phase during loading, which was studied principally using in situ synchrotron X-ray diffraction at the I12 beamline at the Diamond synchrotron. Superelastic β-Ti alloys have the potential to be low weight, economical alternatives to NiTi, Gum metal and Ti-2448 for biomedical, military and aerospace applications. The cubic to orthorhombic stress induced martensitic phase transformation is reversible but has an associated permanent deformation. Reducing the permanent deformation associated with cyclic strain is key to the commercial use of these alloys. The effect of β stability on the SE recovery of Ti-Mo, Ti-Mo-Al and Ti-Mo-O alloys has been investigated. Superelastic behaviour was recreated using cyclic strain whilst being examined under in-situ synchrotron X-ray diffraction. Study of the superelastic phase transformation was carried out in-situ due to the reversible nature of the transformation causing the superelastic phase to largely disappear upon unloading. The superelastic behaviour is shown to be sensitive to β stability and in turn composition and temperature. The addition of aluminium and oxygen can be used to enhance both superelastic recovery and strength. The alloys were designed using Morinaga's orbital design approach combined with Laheurte's average valence electron values, tailoring the bond order (Bo) and electronegativity (Md) in order to alter the method of deformation and phase stability. The third alloy design factors considered concern the effect of alloying on the C' modulus of the β, the ω stability and martensite transformation temperatures. Together these methods, whilst semi-empirical, provide a rational basis for alloy design. Both the lowered stiffness and lower apparent stiffness associated with the design method and the transformation respectively could lead to lowering the stiffness of beta Ti alloys towards that of cortical bone. This would reduce the stiffness mismatch that promotes bone re-absorption around surgical implants, reducing the need for implant replacements. Also, the recent developments in eradicating the residual strain associated with the transformation has led to interest from the aerospace industry for possible (high temperature) damping applications. The Ti-Mo binary mechanical curves show a correlation between the apparent yield stress and composition. An increase in Mo concentration from 7.2 at.% was shown to decrease the yield stress to a minimum at 8.2 at.% Mo, after which the yield stress increased. Out of the 5 binary samples, Ti-8.7Mo at.% showed the best superelastic recovery with a recovery of 1.58% strain for a total strain of 2.3%. The yield stress minima is indicative of the composition at which Ms is closest to room temperature. Ti-8.2Mo at.% has the lowest apparent yield stress and Ti-8.7Mo at.% has the largest SE recovery; this correlates well with the theory that the best superelastic behaviour should be observed for an alloy whose composition places it just above As at room temperature. Al additions, which promote the α phase, were found to significantly improve the superelastic behaviour. Al also acts to suppress the ω phase. The ternary alloy Ti-8.1Mo-5Al at.% showed a 95% strain recovery from a total strain of 1.6% at room temperature. Oxygen behaved as a solution strengthener increasing the yield stress and the associated elastic recovery without impeding the austenitic strain recovery transformation. The addition therefore improved both the apparent yield stress and the SE recovery.
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Knight-Percival, Alexander Stephen. "Low energy super-elastic scattering from laser excited calcium." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/low-energy-superelastic-scattering-from-laser-excited-calcium(e37927e1-97d6-41eb-9a88-06109757c1a0).html.
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Super-elastic scattering measurements were taken from calcium using the spectrometer described in this thesis. Calcium atoms were excited from the 41S0 ground state to the 41P1 excited state using a high resolution continuous wave laser set to a wavelength of 423 nm. A beam of electrons with a well defined energy was directed at the laser excited calcium atoms. The excited state was then described by a set of atomic collision parameters P_lin, gamma and L_perp, found from measuring scattered electrons as a function of scattering angle and energy. The scattering chamber was held at a pressure of 3x10 -7 mbar. A resistively heated oven operating at 800 degrees celsius produced a well collimated calcium atomic beam containing the calcium atoms. The electron gun generated a beam of electrons of well defined momentum, whose energy could be changed from ~5 eV to over 100 eV. At energies less than 20 eV the rate of super-elastic electrons was very low, and so modifications were made to the spectrometer to automate data collection for long operating times without the need for user intervention. A new digitally controlled DC voltage supply was constructed to deliver the correct potentials to the electron-optical elements in the spectrometer. An internal microcontroller enabled supply voltages to be programmed either using the front panel or via an attached computer for automatic optimisation of spectrometer voltages using a simplex algorithm. New data was collected for the collision parameters over the full accessible angular range from 25--140 degrees, at energies of 8, 10 and 65 eV. The data at 8 and 10 eV was taken so as to resolve differences between theoretical models at low energies. Comparisons were made with a relativistic distorted wave calculation, an R-matrix calculation, an R-matrix calculation using B-splines and a convergent close coupling theory. A 2 eV discrepancy was identified in the measured electron energy which was thought to be due to stray fields in the chamber. With this considered, convergent close coupling predictions were found to be in excellent agreement with the experimental data.
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Sang, Robert Thomas, and n/a. "Superelastic Electron Scattering from Laser Excited States of Sodium." Griffith University. School of Science, 1995. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050921.120911.
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This thesis presents the results of a series of experiments in which electrons are superelastically scattered from various laser excited states of sodium. The atoms, once in the optically prepared state, are forced to relax via the superelastic collision with an electron. The rate of detection of superelastically scattered electrons was measured as a function of the laser polarisation which enabled pseudo Stokes parameters to be determined. These pseudo Stokes parameters are functions of both optical pumping parameters and atomic collision parameters. The optical pumping parameters describe the laser-atom interaction and the atomic collision parameters describe the electron-atom collision process. Three different laser excitation mechanisms were used to optically pump the atoms into various excited states. The first of these used a single laser tuned to the 32S 112(F'=2 hyperfine state)-~32P312 transition. The excited atoms underwent a superelastic collision with an electron leaving the atom in the ground state and pseudo Stokes parameters were measured as a function of both scattering angle and incident electron energy. The second superelastic experiment, utilised a folded step excitation mechanism which employed two lasers tuned from the two hypethne states of the 32S112 ground state respectively to the 32P312 excited state. Power broadening effects in the single laser experiment cause the atoms to be optically pumped into the F= 1 hyperfine ground state. The laser powers used were not great enough to power broaden the hyperfine ground states and as such the F'= 1 sublevel effectively acted as a sink. The folded step excitation method enabled the excited state population to be increased so that data at larger scattering angles could be obtained. Stokes parameters from both of these experiments which had an incident energy range of 10eV to 30eV and an angular range of 5°-25° were compared to three current electron-atom scattering theories and previous experimental data. Overall, fair to good agreement was found between theory and experiments for the individual Stokes parameters. Losses of coherence was observed at small scattering angles (50.200) at 20eV and 25eV incident electron energies which were poorly modelled by the three different theories. The third superelastic experiment involved the use of two lasers of specified polarisation to stepwise excite the atoms to the 32D512 excited state. Superelastic collisions with incident electron energies of 20eV from the 32D512-*32P312~312 collision were studied at three different scattering angles and pseudo Stokes parameters for the case where the polarisations of the radiation from the lasers were parallel were measured. The single step and folded step laser-atom interactions for it excitation were modelled using a full quantum electrodynamical treatment so that the optical pumping parameters from the single and folded step experiments could be investigated. Equations of motion were derived in the Heisenberg picture and it is shown that for the single laser case 59 equations of motion are required to fully model the interaction and for the folded step ease 78 equations of motion are required. The results of calculations demonstrated that the optical pumping parameters were sensitive to laser intensity, laser detuning and the Doppler width of the atomic beam. The theoretical quantum electrodynamical calculation results were in good agreement with the experimental results.
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揚偉國 and Wai-kwok Kelvin Yeung. "Gradual scoliosis correction by use of a superelastic alloy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31225469.
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Roberto-Pereira, Francisco Fernando. "Extraction of superelastic parameter values from instrumented indentation data." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290218.
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Interest in superelastic (and shape memory) materials continues to rise, and there is a strong incentive to develop techniques for monitoring of their superelastic characteristics. This is conventionally done via uniaxial testing, but there are many advantages to having a capability for obtaining these characteristics (in the form of parameter values in a constitutive law) via indentation testing. Specimens can then be small, require minimal preparation and be obtainable from components in service. Interrogation of small volumes also allows mapping of properties over a surface. On the other hand, the tested volume must be large enough for its response to be representative of behaviour. Precisely the same arguments apply to more "mainstream" mechanical properties, such as yielding and work hardening characteristics. Indeed, there has been considerable progress in that area recently, using FEM simulation to predict indentation outcomes, evaluating the "goodness of fit" for particular sets of parameter values and converging on a best-fit combination. A similar approach can be used to obtain superelastic parameters, but little work has been done hitherto on sensitivities, uniqueness characteristics or optimal methodologies and the procedures are complicated by limitations to the constitutive laws in current use. The current work presents a comprehensive examination of the issues involved, using experimental (uniaxial and indentation) data for a NiTi Shape Memory Alloy. It was found that it is possible to obtain the superelastic parameter values using a single indenter shape (spherical). Information is also presented on sensitivities and the probable reliability of such parameters obtained in this way for an unknown material.
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Aun, Diego Pinheiro. "Flexible TiO₂ coating on superelastic NiTi alloys for bioapplications." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI098.
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Dans cette étude, nous avons élaboréun revêtementde TiO₂ par sol-gel sur des alliages super-élastiques de NiTi. L’idée générale était de développer couche mince de TiO₂ protectrice et flexible. Le film mince est formé en immergeant les échantillons de NiTi, préalablement chimiquement gravés, dans une solution réactive à 7,5 mm/s, puis en effectuant plusieurs traitements thermiques :un premier traitement thermique à 100 °C pendant 45 minutes dans une atmosphère humide, un deuxième traitement à 110 °C pendant 2 heures dans une atmosphère sèche et enfin un dernier traitement à 500 °C pendant 10 minutes. Les couches minces de TiO₂ ont été caractérisé par de la flexion trois points, par MEB, par MET, par AFM, par GIXRD, par XPS et par de la cartographie Raman. Les résultats de l’étude ont montré un film nanocomposite, avec ~100nmde TiO2 amorphe formé à l’interface externe de la couche et d'un mélange de grains cristallisés de ~10 nm, d'anatase et de rutile à l'interface interne métal/oxyde.Cette hétéro-structure est capable de soutenir 6,4% de déformation sans l’apparition de défauts plastiques majeurs (cloques, fissures...). Une faible concentration de Ni a été observé au niveau de la surface externe des couches minces de TiO₂, ce qui se traduit par une augmentation de la biocompatibilité du matériau. La technique sol-gel a été utilisée pour revêtir des instruments endodontiques de RaCe. Ce deuxième système a été testé à la fois en fatigue pour estimer sa durée de vie, et à la résistance à la corrosion en NaClO, et à des températures correspondant aux transformations de phase. Les résultats ont montré une augmentation statistiquement significative de la durabilité en fatigue, en particulier après les essais de corrosion. L'efficacité de la « coupe », mesurée par une procédure originale, a été similaire aux instruments revêtus et non revêtus. Le traitement thermique n'a pas été suffisant efficient pour modifier de façon significative les températures de transformation de phase : le comportement mécanique d'origine de l'instrument a été maintenuIn this work, a dip-coating sol-gel deposition route was developed to coat superelastic NiTi alloy with a flexible TiO₂ protective layer. The film was formed by emerging the samples at 7.5 mm/s and thermally treating at 100ºC in a humid atmosphere for 45 min, 110ºC in a dry atmosphere for 2 hours and at 500ºC for 10 minutes.The film was first deposited over chemically etched substrates and characterized by SEM, TEM, AFM, GIXRD, XPS, Raman cartographyand three-point bending tests. Results showed that a ~100 nm nanocomposite film constituted of amorphous TiO₂ on the upper half and a mixture of ~10 nm anatase and rutile grains on the oxide/metal interfacewas formed. This film was capable of sustaining up to 6.4% strain without cracking or peeling. A high decrease in the concentration of Ni at the surface was measured, indicating an that an increase in the biocompatibilityof the material was achieved. This route was used to coat RaCe endodontic instruments, which were tested regarding fatigue life, cutting efficiency and corrosion resistance in NaClO. Results showed a statistically significant improvement in fatigue life for the coated instruments, mainly after corrosion tests. Cutting efficiency measured by an original developed technique was similar for coated and uncoated samples
Neste trabalho foi desenvolvida uma rota de deposição sol-gel por imersão para revestirligas de NiTi superelásticas com uma camada protetora e flexível de TiO2. O filmeformado pela emersão de amostras a 7,5 mm/s seguida de tratamentos térmicos a 100ºCpor 45 minutos em atmosfera úmida, 110ºC por 2 horas em atmosfera seca e 500ºC por10 minutos. O filme foi depositado sobre substratos decapados quimicamente ecaracterizados por MEV, MET, AFM, GIXRD, XPS, cartografia Raman e dobramentode três pontos. Resultados mostraram que um filme nanocompósito com ~100 nmconstituído de TiO2 amorfo na metade superior e uma mistura de grãos de 10 a 50 nmde anatase e rutila na interface metal/óxido foi formado. Este filme é capaz de sustentar6,4% de deformação sem trincar ou descamar. Uma grande redução na concentração deNi na superfície foi detectada, indicando um aumento na biocompatibilidade domaterial. A rota foi usada para revestir instrumentos endodônticos de NiTi modeloRaCe 25/0.06 que foram testados em relação à vida em fadiga, eficiência de corte,resistência à corrosão em NaClO. Detectou-se um aumento estatisticamentesignificativo na vida em fadiga, especialmente após os ensaios de corrosão. A eficiênciade corte, medida por um procedimento original desenvolvido, foi similar parainstrumentos revestidos e não revestidos. O tratamento térmico não foi suficiente paraalterar significativamente as temperaturas de transformação de fases, mantendo ocomportamento mecânico original do instrumento
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Yeung, Wai-kwok Kelvin. "Gradual scoliosis correction by use of a superelastic alloy." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23273720.
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Li, Zhiqi. "Experimental investigation on phase transformation of superelastic NiTi microtubes /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?MECH%202002%20LI.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 155-160). Also available in electronic version. Access restricted to campus users.
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Russo, Analisa. "Variation of electrical resistance in superelastic NiTi for sensor applications." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/57875.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 32).
Nickel-Titanium (NiTi) is a most commonly known as a heat-activated shape memory alloy. However, the material sometimes displays a constant-temperature property called "superelasticity." A superelastic material is one which can undergo very high reversible strains due to stress-induced change in crystal structure. In the case of Superelastic NiTi, Martensitic transformation occurs. The two crystal structures differ to the extent that the gradual phase transformation is coupled to a gradual change in resistivity. In fact, resistive sensing is a common characterization technique for shape memory alloys. The unique material properties of superelastic NiTi could also be the basis for creating a resistive sensor that is sensitive enough to measure small displacements, and robust enough to measures large displacements. This study focuses on NiTi which displays superelastic behavior above room temperature. To assess the material's potential as a strain sensing medium, the NiTi wire is shape-set into coil springs which amplify the sensor's net deformation. The relationship between strain and resistance is measured. The study shows that various aspects of the strain-resistance response, including non-linear hysteretic behavior and temperature dependence of electrical resistivity, pose challenges to sensor design. Though the accuracy of the spring sensors is still under development, several recommendations are made with regard to effective device design. In addition, the design of a one-axis strain rate sensor, which differentiates between only two modes of behavior, is explored.
by Analisa Russo.
S.B.
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Gbur, Janet L. "Inclusion Effects on the Lifetime Performance of Superelastic Nitinol Wires." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case153256740897449.
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Fort, Vincent J. "Simulations of the superelastic behavior of nickel-titanium shape memory alloy." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17388.
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Kiesling, Thomas C. "Impact failure modes of graphite epoxy composites with embedded superelastic nitinol." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-09162005-115046/.
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Parkhurst, William T. "Design of a superelastic alloy actuator for a minimally invasive surgical manipulator." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA294440.
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Hossain, Afrin. "Seismic Performance of concrete buildings reinforced with superelastic shape memory alloy rebars." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44785.
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In this study, superelastic shape memory alloy (SMA) rebar was used as reinforcement in the plastic hinge regions of reinforced concrete beams. Twenty different reinforced concrete (RC) moment resisting frames of three different heights (3, 6, and 8-storys) were used in this study where SMA is gradually introduced from level 1 to the top most floor. The frames were designed according to the recent code of (CSA A23.3-04 2004) and assumed to be located in the high seismic zone of Western Canada. Nonlinear static pushover analysis and incremental dynamic analysis, (IDA) considering 20 earthquake records were performed to determine the best distribution of SMA rebars and investigate the seismic performance factors (SPFs). The best distribution of SMA rebars was determined based on the results of the seismic performance of steel and SMA frames obtained from the nonlinear incremental dynamic analysis (IDA) in terms of the maximum inter-story drift ratio (Max.ISDR), maximum residual inter-story drift ratio (Max.RISDR), roof drift ratio (RoofDR) and residual roof drift ratio (RRoofDR). The seismic performance of the SMA RC frames was evaluated where the acceptability of a trial value of the response modification coefficient, R factor was assessed and appropriate values of system overstrength factor, Ω0 and the deflection amplification factor, Cd were determined. The recent FEMA P695 (2009) methodology, was followed for this purpose. The obtained results on SPFs of all individual frames from nonlinear static pushover analysis (POA) and incremental non-linear dynamic analysis, (IDA) represent that the proposed seismic factors were within the range of permissible limit and when subjected to maximum considered earthquake, (MCE) a sufficient margin could be provided against collapse. Steel-SMA-RC frames experienced 4%-17% lower probability of collapse compared to the steel-RC frames.
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Brodie, Robbie. "Characterization of superelastic nitinol wire for application to aortic stent graft design." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30136.
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Aortic stent graft devices are required to treat patients with life-threatening vascular disease. These devices depend on superelastic Nitinol material for their ability to be delivered through a minimally invasive endovascular approach and then to self-expand for long-term implantation at the target site. In this safety-critical application, Nitinol stent components are subjected to challenging in-service conditions in terms of thermo-mechanical loading. Characterization of the material’s response to these loading conditions is therefore essential for its safe and effective implementation in the design of medical devices. This thesis reports material characterization work performed on superelastic Nitinol stent wire under conditions relevant to its in-service application. The product life cycle of Nitinol stent graft components is investigated, highlighting the importance of the material’s bending behaviour and the associated tensile and compressive mechanical responses. With tensile behaviour and test methods already well established for Nitinol, the work first focuses on developing a method for compressive testing of representative Nitinol wire material, building on a previous method to enable testing to higher strains. This allows characterization of the material in compression for thermo-mechanical loading representative of large compaction deformations, in-vivo cycling and different temperatures seen during production, sterilization and implantation. The results also allow a clear understanding of the material’s tension-compression stress-strain asymmetry, which is essential to understanding its bending behaviour. This investigation concludes with a feasibility study into a novel compression test method developed by the author, using short wire samples with high-resolution ‘microtester’ equipment to obtain improved results. The work then focuses on development of a test method for bend testing of thin Nitinol wires to investigate the load response to in-service deformations at relevant test temperatures. This allows characterization of the wire’s load-history dependent bending response, whereby the force exerted at a given deflection during unloading depends on the maximum deflection during loading, with interesting application possibilities for stent components. The testing also allows the material’s temperature dependence, cyclic behaviour and large deformation response in bending to be studied. Following this, full-field strain measurement of thin Nitinol wires in bending is presented, achieved through application of 3-D microscopic Digital Image Correlation(DIC) technology. The development of a novel test method, together with extensive data analysis, provides results for characterization of the material’s complex bending behaviour, allowing new insight to its tension–compression asymmetry, localised deformation, load-unload strain hysteresis and load-history dependence of strain state inbending. This testing provides useful quantitative characterisation data including neutral axis eccentricity at high bend deformations. Finally, Abaqus FEA software is used to investigate the effectiveness of its in-built superelastic constitutive model for representing the Nitinol stent wire’s bending behaviour, and ultimately its suitability for use in stent design and analysis. The uniaxial stress-strain test results are used for input to the model, and then bending simulation results are compared against the experimental results, both in terms of force and strain outputs. Key findings include the model’s inability to represent the strain localisation seen in bending experiments, leading to under-representation of the maximum strains for ‘intermediate’ bend deflections, and also the model’s under-representation of unloading forces at these deflections (unless input parameters are adapted to compensate). Despite these limitations of the model, the cyclic stiffness and strain changes in bending are shown to be reasonably well represented, validating it for its primary use in fatigue analysis of stent components.
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Tian, Feng. "A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1449578210.
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Rutherford, Benjamin Andrew. "Beneficial Tensile Mean Strain Effects on the Fatigue Behavior of Superelastic NiTi." Thesis, Mississippi State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10266594.
Full textAbstract:
In this work, beneficial effects of tensile mean strain on fatigue behavior and microstructure of superelastic NiTi (i.e. Nitinol) are studied. Most applications, such as endovascular stents made with NiTi, are subjected to a combination of constant and cyclic loading; thus, understanding the fatigue behavior of NiTi undergoing mean strain loading is necessary. Cyclic strain-controlled fatigue tests are designed to investigate the effects of tensile mean strain on fatigue of superelastic NiTi. Experimental observations show that combinations of large tensile mean strains and small strain amplitudes improve the fatigue life of superelastic NiTi. This behavior arises from reversible, stress-induced phase transformations. The phase transformations cause “stress plateaus” or strain ranges with no change in stress value. Scanning electron microscopy (SEM) of the fracture surfaces of specimens revealed generally short crack growth. Electron backscatter diffraction (EBSD) found the amount of residual martensite to be about ~8%, regardless of loading conditions.
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Ozbulut, Osman Eser. "Neuro-fuzzy model of superelastic shape memory alloys with application to seismic engineering." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1463.
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Barbero, Bernal Laura Isabel. "Cyclic Behavior of Superelastic Nickel-Titanium and Nickel-Titanium-Chromium Shape Memory Alloys." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4937.
Full textAbstract:
Shape memory alloys (SMAs) are a class of alloys that display the unique ability to undergo nonlinear deformations and return to their original shape when heat is applied or the stress causing the deformation is removed. This unique shape memory characteristic is a result of a martensitic phase-change, which can be temperature induced (shape memory effect) or stress induced (superelastic effect).
In this study, the cyclical behavior of NiTi, a binary shape memory alloy, is compared to the cyclical behavior of NiTiCr, a ternary SMA. The purpose of this study is to compare the behavior of a 0.085-in. diameter NiTiCr wire with the behavior of the same size NiTi wire to determine whether ternary SMAs are more viable ways to take advantage of the unique properties of SMAs for seismic applications. The experimental results showing the superelastic behavior of these alloys under cyclical tensile loading are summarized with attention to the effects of annealing temperature, strain rate, and cyclical training on the stress-strain hysteresis, maximum recoverable strain and equivalent viscous damping.
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Andrawes, Bassem Onsi. "Seismic Response and Analysis of Multiple Frame Bridges Using Superelastic Shape Memory Alloys." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6914.
Full textAbstract:
The feasibility of using superelastic shape memory alloys in the retrofit of multiple frame bridges is investigated. First, three shape memory alloy constitutive models with various levels of complexity are compared in order to determine the significance of including subloops and cyclic loading effects on the structural response. The results show that the structural response is more sensitive to the shape memory alloys strength degradation and residual deformation than the sublooping behavior. Next, two parametric studies are conducted to explore the sensitivity of hinge opening to the mechanical behavior of the superelastic shape memory alloys. The first study is focused on the hysteretic properties of the alloy that could vary depending on the chemical composition or the manufacturing process of the alloy, while the second study targets the changes in the mechanical behavior of shape memory alloys resulting from the variability in the ambient temperature. The results show that the hysteretic behavior of shape memory alloys has only a slight effect on the bridge hinge opening as long as the recentering property is maintained. A detailed study on the effect of temperature shows that a reduction in the ambient temperature tends to negatively affect the hinge opening while an increase in temperature results in a slight improvement. Next, a parametric study is conducted to examine the effectiveness of shape memory alloy retrofit devices in limiting hinge openings in bridges with various properties. In addition, a comparison is made with other devices such as conventional steel restrainers, metallic dampers, and viscoelastic solid dampers. The results illustrate that superelastic shape memory alloys are superior in their effectiveness compared to other devices in the case of bridges with moderate period ratios and high level of ductility, especially when subjected to strong earthquakes.
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Rahmanian, Rasool. "Optimizing mechanical stiffness of shape memory and superelastic alloys by introducing engineering porosity." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1399370484.
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Koludrovich, Michael. "Design, Analysis, and Experimental Evaluation of a Superelastic NiTi Minimally Invasive Thrombectomy Device." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1399370551.
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Kiely, Lewis. "Review of new methods of modelling plasticity." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/9320.
Full textAbstract:
Recent short pulse (femtosecond) laser experiments have shown the existence
of a so called superelastic precursor for short time periods after shock wave
formation. The superelastic precursor is characterised as having amplitude far
greater than the Hugoniot Elastic limit.
This work reviews the current orthotropic thermoelastic plastic-damage model
developed at Cranfield University, which includes the ability to model high
velocity, shock wave forming impacts. The current model is unable to reproduce
the superelastic precursor. Recent methods of looking at plasticity are reviewed
and model improvements are suggested to enable the Cranfield model to
reproduce superelastic precursor waves. The methods investigated are both
dislocation based as it is determined that it is necessary to model deformation
on the microscale in order to achieve reproduction of phenomena on the
timescales of the early stages of shock wave formation and propagation. The
methods investigated are the so-called self-organisation of dislocations and a
mobile and immobile dislocation method proposed by Mayer.
The plasticity part of the model proposed by Mayer is suggested for further
investigation, including implementation into the DYNA 3D hydrocode which
contains the current Cranfield model, to numerically asses the models
capabilities. Similar, the self-organisation model is put forward for further
numerical analysis.
Further, calculation of the continuum Cauchy stress using purely atomistic
variables is investigated in the form of the virial stress. It is determined that the
virial stress calculation is unsuitable for modelling shock waves, however an
alternative atomistic stress calculation which is more suited to shock waves is
discussed. It is proposed that this stress calculation could be used to investigate
the stresses contained within the thin shock front.
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Taheri, Andani Masood. "Constitutive Modeling of Superelastic Shape Memory Alloys Considering RateDependent Non-Mises Tension-torsion Behavior." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1371577037.
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Gilmore, Paul. "A Morphing Extrusion Die for Manufacturing of Thermoplastic Hoses." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429799958.
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Abdulridha, Alaa. "Performance of Superelastic Shape Memory Alloy Reinforced Concrete Elements Subjected to Monotonic and Cyclic Loading." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24168.
Full textAbstract:
The ability to adjust structural response to external loading and ensure structural safety and serviceability is a characteristic of Smart Systems. The key to achieving this is through the development and implementation of smart materials. An example of a smart material is a Shape Memory Alloy (SMA).
Reinforced concrete structures are designed to sustain severe damage and permanent displacement during strong earthquakes, while maintaining their integrity, and safeguarding against loss of life. The design philosophy of dissipating the energy of major earthquakes leads to significant strains in the steel reinforcement and, consequently, damage in the plastic hinge zones. Most of the steel strain is permanent, thus leading to large residual deformations that can render the structure unserviceable after the earthquake. Alternative reinforcing materials such as superelastic SMAs offer strain recovery upon unloading, which may result in improved post-earthquake recovery. Shape Memory Alloys have the ability to dissipate energy through repeated cycling without significant degradation or permanent deformation. Superelastic SMAs possess stable hysteretic behavior over a certain range of temperature, where its shape is recoverable upon removal of load. Alternatively, Martensite SMAs also possess the ability to recover its shape through heating. Both types of SMA demonstrate promise in civil infrastructure applications, specifically in seismic-resistant design and retrofit of structures.
The primary objective of this research is to investigate experimentally the performance of concrete beams and shear walls reinforced with superelastic SMAs in plastic hinge regions. Furthermore, this research program involves complementary numerical studies and the development of a proposed hysteretic constitutive model for superelastic SMAs applicable for nonlinear finite element analysis. The model considers the unique characteristics of the cyclic response of superelastic materials.
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Vieira, Camilla Ivini Viana. "Avaliação de superelasticidade e deformação das molas fechadas de níquel-titânio sob diferentes ativações /." Araraquara : [s.n.], 2011. http://hdl.handle.net/11449/99803.
Full textAbstract:
Orientador: Lídia Parsekian MartinsBanca: Luiz Gonzaga Gandini Junior
Banca: Renata Rodrigues de Almeida Pedrin
Resumo: Avaliar se molas fechadas de níquel-titânio de diferentes marcas comerciais Morelli®, Orthometric®, Ormco®, GAC® apresentam comportamento superelástico (SE), se o plateau de força produzido condiz com o fornecido pelo fabricante e determinar quais são os percentuais de deformação das molas testadas. Materiais e Métodos: Dois artigos científicos foram redigidos e utilizados para a avaliação dos propósitos apresentados e para compilação de um pequeno guia clínico. Resultados: A maioria das molas mostrou-se superelásticas a partir da ativação inicial de 400%, apenas um subgrupo não apresentou comportamento superelástico em nenhuma das ativações. Os plateaus SE fornecidos pelos fabricantes do grupo 1 e subgrupo 3C não correspondem aos encontrados nesse estudo. Para os subgrupos 3A, 4E e 4A as molas apresentaram o plateau correspondente com o fabricante a 600%, 500% e a 400% de ativação inicial, respectivamente. Nos subgrupos 2A, 2B, 4B, 4C, 4D, 4F e 4G os plateaus SE corresponderam aos valores fornecidos pelo fabricante de 600 a 800%, 400 a 500%, 600 a 800%, 400 a 700%, 400 a 600%, 400 a 600% e de 500 a 700% de ativação inicial. A deformação das molas do subgrupo 1A e 1B não foram diferentes de 400 a 700% e 400 a 800% de ativação respectivamente. A deformação das molas do subgrupo 2A e 2B foram iguais de 400 a 700% e 400% a 600% de ativação 20 respectivamente. As deformações causadas de 400 a 700% de ativação no subgrupo 3A foram iguais. No subgrupo 3C, as deformações ocorridas em 600% e 700% de ativação foram iguais. No subgrupo 4A, as deformações ocorridas de 400 a 800% de ativação foram iguais. No subgrupo 4B, 4D, 4C e 4E, todas as deformações foram iguais. No subgrupo 4G as deformações foram iguais de 500 a 800%. Conclusões: A maioria das molas mostrou-se SE a partir da ativação inicial de 400%... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: To verify whether different nickel-titanium closed coil springs Morelli®, Orthometric®, Ormco®, GAC® have superelastic (SE) behavior, if the force plateaus are consistent with the information provided by the manufacturer and to determine the percentage of deformation according to initial activation. Materials and Methods: Two scientific papers were compiled for evaluation. Results: Most of the subgroups showed SE behavior when activated 400% and one subgroup was not SE. The plateaus SE provided by manufacturers of a group and subgroup 3C do not correspond to those found in this study. For the subgroups 3A,4A and 4E springs showed a plateau corresponding to the manufacturer with 600%, 500% and 400% of initial activation, respectively. In subgroups 2A, 2B, 4B, 4C, 4D, 4F and 4G plateaus corresponded to the values provided by the manufacturer from 600 to 800%, 400 to 500%, 600 to 800%, 400 to 700%, 400 to 600 %, 400 to 600 and from 500% to 700% of initial activation. The subgroups behaved differently when it comes to deformation: the deformations of subgroup 1A and 1B were the same: from 400 to 700% and from 400 to 800% activation, respectively. The deformations on subgroups 2A and 2B were the same: from 400 to 700% and from 400 to 600% of activation, 23 respectively. The deformations on subgroup 3A were the same from 400 to 700% of activation, while in subgroup 3C, the deformations were the same from 600 to 700% of activation. In subgroup 4A, the deformations were the same from 400 to 800% activation. In the subgroups 4B, 4D, 4C and 4E, deformations were equal on all activations, while on subgroup 4G deformations were similar from 500 to 800%. Conclusions: Most of the springs were SE from 400% of activation on. In most subgroups, the deformations, up to 700% of initial activation, were the same. The force plateaus were inversely proportional on initial activation
Mestre
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Sargin, Irmak. "Effect Of Stress Assisted Aging On Superelastic Behavior Of A Hot-rolled Niti Shape Memory Alloy." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613184/index.pdf.
Full textAbstract:
Effect of stress-assisted aging on stress induced martensitic transformation in hot-rolled
Ni-rich 50.7at. Ni%-Ti alloy has been investigated. Alloys are aged freely and under 20
MPa, 100 MPa, and 200 MPa stress at 400
o
C for 90 minutes. Aging procedure affected
both stress-induced and thermally induced transformation behavior. Superelasticity
behavior is correlated with the multistep transformation in aged Ni-rich NiTi alloys and the
aging stress level is found to be effective. Relative to the free aged alloy, the alloy aged
under 20 MPa exhibited a slight and the alloy aged under 100 MPa exhibited a
considerable reduction, whereas the alloy aged under 200 MPa exhibited an increase in the
critical transformation stress. DSC studies have shown that the transformation is multistep
for freely aged and aged under 20 MPa alloys, whereas it is single step and two-step for
alloys aged under 100 MPa and 200 MPa, respectively, and this has been attributed to the
effect of stress on nucleation and growth rates. As a result of the different response
mechanisms to the applied stress upon loading during superelasticity testing, the recovered
strain amounts varied considerably depending on the aging conditions and the test
temperatures.
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Hedayati, Dezfuli Farshad. "Hysteretic behaviour of steel- and fibre-reinforced elastomeric isolators fitted with superelastic shape memory alloy wire." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/53019.
Full textAbstract:
Among different types of earthquake protective mechanisms, elastomeric base isolators, also called rubber bearings (RBs), are one of the most well-known systems that are widely used in buildings and bridges. They can regulate the seismic response of structures, increase the public safety, and reduce the cost of repair and rehabilitation by providing lateral flexibility and dissipating the earthquake’s energy. RBs consist of elastomeric layers which are reinforced with steel shims or fibre-reinforced polymer composites. Seeking performance improvements, as well as cost and weight reduction led scientists to introduce different types of RBs. However, most RBs possess weaknesses such as limited shear strain capacity, un-recovered residual deformation, and instability due to large deformations. Using superelastic (ability to regain original shape upon unloading) shape memory alloy (SMA) in the form of wire, bar, or spring is a solution to partially overcome the aforementioned limitations. Its unique characteristics such as a flag-shaped hysteresis with zero residual deformation, superelastic effect (up to 13.5% recoverable strain) and a suitable fatigue property make it an ideal candidate for such applications. Objectives of this thesis are to propose a new generation SMA wire-based RBs (SMA-RB) and develop a novel constitutive model for such smart isolators in order to accurately capture their shear hysteretic behaviour. With the purpose of evaluating the performance of SMA-RBs in structural applications, the seismic fragility of a highway bridge isolated by SMA-RBs was assessed. First, a number of scaled carbon fibre-reinforced elastomeric isolators (C-FREIs) were manufactured and tested. Then, based on the experimental observations, numerical simulations were generated using finite element method (FEM). Results showed that incorporating SMA wires into natural and high-damping rubber bearings (NRB, HDRB) slightly improves the re-centring capability and energy dissipation capacity. However, equipping lead rubber bearing (LRB) with double cross SMA wires significantly reduces the residual deformation and noticeably enhances the energy damping property. It was also depicted that the developed hysteresis of SMA model can be characterized by three stiffnesses and two shear strain limits upon activation of SMA wires. Findings revealed that SMA wires can increase the reliability of elastomeric bearings and bridge system.Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate
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Manjeri, Radhakrishnan. "Low Temperature and Reduced Length Scale Behavior of Shape Memory and Superelastic NiTi and NiTiFe Alloys." Master's thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6227.
Full textAbstract:
Shape memory and superelastic applications of NiTi based alloys have typically been limited to near room temperature or to bulk length scales. The objective of this work is two-fold: first, to investigate shape memory behavior at low temperatures in the context of the R-phase transformation in NiTiFe alloys by recourse to arc-melting, differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and mechanical testing at low temperatures; and second, to investigate superelasticity and two-way shape memory behavior at reduced length scales in the context of NiTi by recourse to micro-compression, micro-indentation and TEM studies. Selected compositions of ternary NiTiFe shape memory alloys were arc-melted and thermo-mechanically processed to investigate the influence of composition and processing parameters on the formation of the R-phase. The methodology used for the processing and characterization of the alloys was established and included microprobe analysis, DSC, TEM and mechanical testing. No phase transformation was observed in alloys with Fe content in excess of 4 at.%. The rmo-mechanical treatments facilitated the formation of the R-phase in Ni-rich alloys. The range of the transformation between the R-phase and austenite, and the hysteresis associated with it were influenced by the distribution and size of metastable Ni4Ti3 precipitates. The investigation of the microstructural, thermal and mechanical properties of the R-phase transformation in NiTiFe alloys revealed a complex dependence of these properties on processing parameters. The present work also highlighted the hitherto unexplored competition between the two inelastic deformation modes operating in the R-phase (detwinning and stress-induced transformation) and establishedthe preference of one mode over the other in stress-temperature space. The complete micromechanical response of superelastic NiTi was examined by performing careful micro-compression experiments on single crystal pillars of known orientations using a nanoindenter tip. Specifically, the orientation dependence of the elastic deformation of austenite, the onset of its transformation to martensite, the gradient and the hysteresis in the stress-strain response during transformation, the elastic modulus of the stress-induced martensite and the onset of plasticity of the stress-induced martensite were analyzed in separate experiments. A majority of the results were explained by recourse to a quantitative determination of strains associated with austenite grains transforming to martensite variants or twinning in martensite. Microstructural studies were also performed on a micro-indentation trained NiTi shape memory alloy specimen to understand the mechanisms governing the two-way shape memory effect. In situ TEM studies at temperature on specimens obtained at different depths below the indent showed the presence of retained martensite along with the R-phase. Previously, while such two-way shape memory behavior has typically been associated with large dislocation densities, this work provides evidence of the role of retained martensite and the R-phase in cases with reduced dislocation densities. Funding support for this work from NSF (CAREER DMR-0239512), NASA (NAG3-2751) and SRI is acknowledged.Ph.D.
Doctorate
Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
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Vaidyanathan, Rajan 1973. "Mechanical properties of superelastic and shape-memory NiTi and NiTi-TiC composites investigated by neutron diffraction." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84744.
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Vieira, Camilla Ivini Viana [UNESP]. "Avaliação de superelasticidade e deformação das molas fechadas de níquel-titânio sob diferentes ativações." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/99803.
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Made available in DSpace on 2014-06-11T19:30:21Z (GMT). No. of bitstreams: 0
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vieira_civ_me_arafo.pdf: 671993 bytes, checksum: 04b491c600f4489b33e816b6cd2dd3e6 (MD5)Avaliar se molas fechadas de níquel-titânio de diferentes marcas comerciais Morelli®, Orthometric®, Ormco®, GAC® apresentam comportamento superelástico (SE), se o plateau de força produzido condiz com o fornecido pelo fabricante e determinar quais são os percentuais de deformação das molas testadas. Materiais e Métodos: Dois artigos científicos foram redigidos e utilizados para a avaliação dos propósitos apresentados e para compilação de um pequeno guia clínico. Resultados: A maioria das molas mostrou-se superelásticas a partir da ativação inicial de 400%, apenas um subgrupo não apresentou comportamento superelástico em nenhuma das ativações. Os plateaus SE fornecidos pelos fabricantes do grupo 1 e subgrupo 3C não correspondem aos encontrados nesse estudo. Para os subgrupos 3A, 4E e 4A as molas apresentaram o plateau correspondente com o fabricante a 600%, 500% e a 400% de ativação inicial, respectivamente. Nos subgrupos 2A, 2B, 4B, 4C, 4D, 4F e 4G os plateaus SE corresponderam aos valores fornecidos pelo fabricante de 600 a 800%, 400 a 500%, 600 a 800%, 400 a 700%, 400 a 600%, 400 a 600% e de 500 a 700% de ativação inicial. A deformação das molas do subgrupo 1A e 1B não foram diferentes de 400 a 700% e 400 a 800% de ativação respectivamente. A deformação das molas do subgrupo 2A e 2B foram iguais de 400 a 700% e 400% a 600% de ativação 20 respectivamente. As deformações causadas de 400 a 700% de ativação no subgrupo 3A foram iguais. No subgrupo 3C, as deformações ocorridas em 600% e 700% de ativação foram iguais. No subgrupo 4A, as deformações ocorridas de 400 a 800% de ativação foram iguais. No subgrupo 4B, 4D, 4C e 4E, todas as deformações foram iguais. No subgrupo 4G as deformações foram iguais de 500 a 800%. Conclusões: A maioria das molas mostrou-se SE a partir da ativação inicial de 400%...
To verify whether different nickel-titanium closed coil springs Morelli®, Orthometric®, Ormco®, GAC® have superelastic (SE) behavior, if the force plateaus are consistent with the information provided by the manufacturer and to determine the percentage of deformation according to initial activation. Materials and Methods: Two scientific papers were compiled for evaluation. Results: Most of the subgroups showed SE behavior when activated 400% and one subgroup was not SE. The plateaus SE provided by manufacturers of a group and subgroup 3C do not correspond to those found in this study. For the subgroups 3A,4A and 4E springs showed a plateau corresponding to the manufacturer with 600%, 500% and 400% of initial activation, respectively. In subgroups 2A, 2B, 4B, 4C, 4D, 4F and 4G plateaus corresponded to the values provided by the manufacturer from 600 to 800%, 400 to 500%, 600 to 800%, 400 to 700%, 400 to 600 %, 400 to 600 and from 500% to 700% of initial activation. The subgroups behaved differently when it comes to deformation: the deformations of subgroup 1A and 1B were the same: from 400 to 700% and from 400 to 800% activation, respectively. The deformations on subgroups 2A and 2B were the same: from 400 to 700% and from 400 to 600% of activation, 23 respectively. The deformations on subgroup 3A were the same from 400 to 700% of activation, while in subgroup 3C, the deformations were the same from 600 to 700% of activation. In subgroup 4A, the deformations were the same from 400 to 800% activation. In the subgroups 4B, 4D, 4C and 4E, deformations were equal on all activations, while on subgroup 4G deformations were similar from 500 to 800%. Conclusions: Most of the springs were SE from 400% of activation on. In most subgroups, the deformations, up to 700% of initial activation, were the same. The force plateaus were inversely proportional on initial activation
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Dubinskiy, Sergey. "Ti-Nb-(Zr,Ta) superelastic alloys for medical implants : thermomechanical processing, structure, phase transformations and functional properties." Mémoire, École de technologie supérieure, 2013. http://espace.etsmtl.ca/1266/1/DUBINSKIY_Sergey.pdf.
Full textAbstract:
Le but de ce projet est de développer une nouvelle classe de matériaux d'implants orthopédiques, qui combinerait une excellente biocompatibilité du titane pur avec une compatibilité biomécanique exceptionnelle d'alliages à mémoire de forme Ti-Ni. Les candidats les plus appropriés pour un tel rôle sont les alliages à mémoire de forme Ti-Nb-Zr et Ti-Nb-Ta de type beta métastable. Cette classe de matériaux a été développée tout récemment et l'influence du traitement thermomécanique sur leur structure et leurs propriétés fonctionnelles ne faisaient pas encore objet d'aucune étude approfondie. Par conséquent, ce projet est axé sur les relations entre la composition, la microstructure et les propriétés fonctionnelles des alliages superélastiques Ti-Nb-Zr et Ti-Nb-Ta pour applications biomédicales. L'objectif principal est d'améliorer les propriétés fonctionnelles de ces alliages,
plus particulièrement les propriétés superélastiques et la résistance à la fatigue, grâce à l'optimisation de la composition des alliages et de leur traitement thermomécanique.
Premièrement, cette thèse prouve que la structure et les propriétés fonctionnelles des alliages à mémoire de forme à base de Ti-Nb peuvent être efficacement contrôlées par un traitement thermomécanique, y compris par la déformation à froid suivie de traitement thermique de recuit et de vieillissement. Il est également démontré que la formation d’une structure nano sous-granulaire mène à une amélioration significative de la superélasticité et de la résistance à la fatigue de ces alliages. L'influence du vieillissement sur la cinétique de précipitation de la phase ω et, par conséquent, sur les propriétés fonctionnelles des alliages Ti-Nb-Zr et Ti-Nb-Ta est également observée.
Basant sur les résultats obtenus, les régimes du traitement thermomécanique optimisé résultant en une meilleure combinaison des propriétés fonctionnelles sont recommandés pour chaque alliage, d’un point de vue de matériau pour implants orthopédiques.
Deuxièmement, un dispositif de traction miniature pour une étude in situ à basse température dans la chambre d’un diffractomètre à rayons X a été développé et utilisé. Une étude comparative sur les caractéristiques des transformations et de l'évolution du réseau cristallin dans des conditions du contrôle de déformation et de balayage en
température entre -150 et +100oC a été réalisée in situ. Les paramètres de la maille cristalline des phases β et α” ont été calculés dans une plage de température étudiée, ce que nous a permis de conclure que plus la température est élevée, plus la déformation qui accompagne la transformation des phases α”→β est faible. On a également constaté que le chargement à basse température mène à la formation additionnelle et la réorientation de la phase α”, tandis que l'application de la charge lors du chauffage modifie la séquence des transformations. L’élargissement et le rétrécissement réversible des pics de la phase β qui
sont observées lors du balayage en température sont le résultat direct de l’apparition et de la disparition des micro-contraintes causées par la transformation martensitique thermoélastique réversible.
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Roy, Alexander M. "Prediction of low and high cycle multiaxial fatigue of superelastic nitinol stents via uniaxial fatigue based equations." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527412.
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Puffer, Andrew James. "Design and Testing of a Minimally Invasive Blood Clot Removal Device Constructed With Elements of Superelastic Nitinol." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1399558753.
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Hasan, Mahamudul. "In-situ martensite texture evolution and phase fractions of superelastic NiTi upon tensile loading using synchrotron hard x-ray diffraction." Bochum Europ. Univ.-Verl, 2007. http://deposit.d-nb.de/cgi-bin/dokserv?id=3013895&prov=M&dok_var=1&dok_ext=htm.
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Pursehouse, James. "Electron and photon interactions in magnesium, calcium and rubidium." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/electron-and-photon-interactions-in-magnesium-calcium-and-rubidium(cf98e2a6-ae7d-45b9-91c4-33f148a5678e).html.
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In the experiments detailed in this thesis, a series of scattering experiments were conducted in a versatile scattering chamber. In order to conduct these experiments, various electronic equipment was designed and built, including new computer controlled electron analyser power supplies. This new equipment was tested, adopted in this work, and is described in this thesis. The superelastic scattering technique was used on magnesium atoms to obtain a set of atomic collision parameters (ACPs), which describe the interaction. This was achieved by exciting a beam of magnesium atoms to the 3(1)P(1) excited state using resonant laser radiation around 285 nm, and using an electron beam with well defined momentum to de-excite the atoms. The momentum of the outgoing electrons was measured as the polarisation and scattering angle were varied, to obtain the ACPs. These measurements were carried out over an angular range of 30 degrees to 120 degrees and with incident energies equivalent to 35 eV, 40 eV, 45 eV, and 55 eV. A set of theoretical data was compared to the experimental results and found to be reasonably accurate at describing the interaction. Laser-aligned and ground-state (e,2e) ionisation measurements were taken from the 4(1)S(0) and 4(1)P(1) states of calcium. The measurements were taken with the energy of the scattered and ejected electrons set at 30 eV, and with one outgoing electron angle set to 45 degrees. The differential cross section was determined for a range of angles of the second electron, ranging from 30 degrees to 65 degrees. The incident and outgoing electron momenta were all defined in the same plane with the laser polarisation being in a plane perpendicular to the incident electron. The laser aligned (e,2e) measurements were compared to two theoretical models, one of which (a 3DW model) predicted an identically zero cross section when the laser polarisation was perpendicular to the scattering plane. The other model (a TDCC model) predicted a non-zero cross section, in agreement with the experiment. Simultaneous time-resolved two-colour photoionisation from the 5(2)P(3/2) and 6(2)P(3/2) states of rubidium was also conducted. These experiments investigated two pathways to creating 0.36 eV photoelectrons from rubidium. Photoelectrons were produced by either using laser radiation at ~780 nm to resonantly excite atoms to the 5(2)P(3/2) state followed by laser radiation at ~420 nm to ionise the atoms, or laser radiation at ~420 nm was used to resonantly excite atoms to the 6(2)P(3/2) state followed by radiation at ~780 nm which then ionised the atoms. Ionisation differential cross sections were measured over a full 360 degrees by rotating the laser polarisation vectors. By selectively detuning the laser beam so as to select individual ionisation pathways, and then by tuning both lasers to resonance, quantum interferences between the pathways that lead to ionisation were observed.
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Jawed, Syed Faraz. "Design, microstructure and properties of metastable beta-type biomedical titanium alloys." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2020. https://ro.ecu.edu.au/theses/2380.
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Many existing implant biomaterials including cobalt-chromium alloy, stainless steel, Ti-6Al-4V and commercially pure titanium have all been shown to demonstrate mechanical incompatibility, poor osseointegration and/or cause cytotoxic effects on the human body after some years of application, leading to revision surgery in most cases. Consequently, there is an immediate need for an enduring biomaterial that displays good mechanical properties and possesses biocompatibility and corrosion resistance, in order to reduce rates of revision surgeries. In this PhD work, based on the 𝐵𝑜̅̅̅̅-𝑀𝑑̅̅̅̅̅, 𝑒/𝑎̅̅̅̅̅-𝛥𝑟̅̅̅ and BF-d-electron superelastic theoretical relationships four new series of quaternary Ti-25Nb-8Zr-xCr, Ti-25Nb-xSn-yCr, Ti26Nb-xMn-yZr and Ti-25Nb-xMn-ySn alloys have been designed for the first time. These designed alloys were produced using the cold crucible levitation melting method, where the effect of balanced combination of β-isomorphous (Nb), β-eutectic (Cr, Mn) and neutral (Zr, Sn) elements on phase transformation, β-phase stability and mechanical properties of the alloys are investigated.
Microstructural investigations of Ti-25Nb-8Zr-xCr (x = 0, 2, 4, 6, 8) demonstrate a single β phase, with the exception of Ti-25Nb-8Zr-0Cr which shows dual α" and β phases. Furthermore, the addition of Cr is shown to be effective in achieving a single β phase where suppressing the formation of α" phase. As the content of Cr increases, the yield strength (382-773 MPa) and hardness (1.91-2.63 GPa) also increase in Ti-25Nb-8Zr-xCr alloys. Notably, all the investigated alloys demonstrated significant strain hardening rates.
The Ti-25Nb-xSn-yCr (x = 1, 3, 5 wt% and y= 2, 4 wt%) alloys demonstrated only β phase in their microstructures. It is of note that all Ti-25Nb-xSn-yCr alloys displayed large plasticity of ~80% without failure during mechanical testing. Yield strength, hardness and elastic modulus were (314-463) MPa, (2.36-1.93) GPa and (66-78) GPa, respectively. Ti-25Nb-1Sn-2Cr possessed the higher values of wear resistance indices (i.e. H/E and H ) as compared to commercially pure titanium and Ti-6Al-4V.
The Microstructural features of Ti-26Nb-xZr-yMn (x = 4, 7, 10 wt% and y = 3, 5 wt%) alloys revealed a monolithic β phase. Notably, none of the alloys displayed failure and demonstrated substantial true plasticity of ~160% during mechanical compression testing. Yield strength, hardness and dislocation density were (609-451) MPa, (242-207) HV and (2.45×10 ) m 15 15 -0.4×10 -2 , respectively. Additionally, Ti-26Nb-4Zr-5Mn demonstrates good strain hardening ability and electrochemical kinetics in terms of high strain hardening indices (0.42 and 0.09) and small corrosion current density (0.839 nA/cm 2 ), respectively.
In Ti-25Nb-xMn-ySn (x = 2, 4 wt% and y = 1, 5 wt%) alloys, it was found that only Ti-25Nb2Mn-1Sn displayed dual β and α" phases while others showed a monolithic β phase. Yield strength, hardness and superelastic recovery ratio were (710-563) MPa, (244-207) HV and (9080) %, respectively. It is of noteworthy; Ti-25Nb-4Mn-1Sn displays the low elastic modulus and high energy absorption.
The results demonstrate that among the investigated alloys Ti-25Nb-8Zr-4Cr, Ti-25Nb-1Sn2Cr, Ti-26Nb-4Zr-5Mn and Ti-25Nb-4Mn-1Sn display superior combination of mechanical properties making them suitable materials for implant applications.
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Sousa, Vagner Candido de. "Effects of superelastic shape memory springs on the aeroelastic behavior of a typical airfoil section: passive vibration attenuation and energy harvesting applications." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-11032017-123620/.
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The modeling, analysis and experimental verification of a two-degree-of-freedom typical aeroelastic section with superelastic shape memory alloy springs are presented. The focus is to investigate the effects of the phase transformation of the shape memory alloy springs on the flutter and post-flutter behaviors of the typical section. The shape memory alloy phase transformation kinetics is described by a modified version of well-known phenomenological models. The shape memory alloy spring model is based on classical spring design (with the pure shear assumption) and modified to account for the nonlinear effects of phase transformation. The cross-section of the shape memory alloy wire is represented by a linear radial distribution of shear strain and nonlinear radial distributions of shear stress and martensitic fraction. The equations of motion of a linear typical section are modified to include the shape memory alloy springs. A linear unsteady aerodynamic model is employed to determine the aerodynamic loads. The proposed model is cast into state-space representation and solved with a Runge-Kutta method. It is numerically and experimentally shown that the phase transformation of shape memory alloy springs can be effectively exploited to enhance the aeroelastic behavior of a typical section by replacing unstable flutter oscillations by stable oscillations of acceptable amplitudes over a range of airflow speeds, providing a useful method of passive aeroelastic control. Since the modified aeroelastic behavior is attractive for wind energy harvesting purposes, electromechanical coupling is also modeled in the plunge degree-of-freedom along with a resistive load in the electrical domain for electrical power estimation. The exploitation of the shape memory alloy phase transformation is more attractive for airfoil-based wind energy harvesting performance than the use of typical concentrated nonlinearities (e.g., hardening steel) in terms of enhanced electrical power output.A modelagem, análise e verificação experimental de uma seção típica aeroelástica com dois graus de liberdade e molas com memória de forma superelásticas são apresentadas. O foco é investigar os efeitos da histerese pseudoelástica das molas com memória de forma nos comportamentos de flutter e pós-flutter da seção típica. A cinética das transformações de fase nas molas com memória de forma é descrita por uma versão modificada de modelos fenomenológicos amplamente conhecidos. O modelo de molas helicoidais com memória de forma é baseado em teoria clássica de molas (com a hipótese de cisalhamento puro) e modificado para representar os efeitos não lineares de transformação de fase. A seção transversal do fio da mola com memória de forma é representada por uma distribuição radial e linear de deformações de cisalhamento e por distribuições radiais e não lineares de tensões cisalhantes e de frações martensíticas. As equações de movimento de uma seção típica linear são modificadas para incluir as molas com memória de forma. Um modelo aerodinâmico linear não estacionário é utilizado para se determinar as cargas aerodinâmicas. O modelo proposto é representado em espaço de estados e resolvido com um método Runge-Kutta. Mostra-se, numérica e experimentalmente, que a histerese pseudoelástica de molas com memória de forma pode ser efetivamente explorada para melhorar o comportamento aeroelástico de uma seção típica ao transformar oscilações instáveis de flutter em oscilações estáveis e de amplitudes aceitáveis em uma faixa de velocidades do escoamento, provendo um método útil de controle aeroelástico passivo. Como o comportamento aeroelástico modificado (pela histerese pseudoelástica) é atrativo para a coleta de energia do escoamento, um acoplamento eletromecânico é modelado no grau de liberdade de deslocamento linear, juntamente com uma carga resistiva no domínio elétrico do problema para se estimar a potência elétrica gerada. A exploração da histerese pseudoelástica das molas com memória de forma é mais atrativa para a performance da coleta aeroelástica de energia do que o uso de não linearidades concentradas típicas (como o enrijecimento não linear do aço) em termos de melhoria na potência elétrica gerada.
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Herron, Adam David. "Mesoscale Modeling of Shape Memory Alloys by Kinetic Monte Carlo–Finite Element Analysis Methods." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8261.
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A coupled kinetic Monte Carlo – Finite Element Analysis (kMC–FEA) method is developed with a numerical implementation in the Scalable Implementation of Finite Elements at NASA (ScIFEN). This method is presented as a mesoscale model for Shape Memory Alloy (SMA) material systems. The model is based on Transition State Theory and predicts the nonlinear mechanical behavior of the 1st order solid–solid phase transformation between Austenite and Martensite in SMAs. The kMC–FEA modeling method presented in this work builds upon the work of Chen and Schuh [1, 2]. It represents a “bottom-up” approach to materials modeling and could serve as a bridge for future studies that attempt to link ab initio methods with phenomenological findings in SMA systems. This thesis presents the derivation of the kMC–FEA model, which is then used to probe the various responses expected in SMAs and verify the influence of model parameters on simulation behavior. In a departure from the work of Chen and Schuh, the thermodynamic derivation includes an elastic transformation energy term, which is found to be a significant fraction of the total transformation energy and play an important role in the evolution of a simulation. Theoretical predictions of the model behavior can be made from this derivation, including expected transformation stresses and temperatures. A convergence study is presented as verification that the new elastic energy term proposed in this model is a reasonable approximation. A parameter sensitivity study is also presented, showing good agreement between theoretical predictions and the results of a full-factorial numerical exploration of model outputs. Model simulation demonstrates the emergence of the shape memory effect, an important SMA behavior not shown by Chen and Schuh, along with the expected superelastic effect and thermal hysteresis. Further exploration of simulated model outputs presented in this work involves comparison with experimental data and predicted output values obtained from a separate phenomenological constitutive model. This comparison shows that the kMC–FEA method is capable of reproducing qualitative, but not yet quantitative, responses of real SMA material systems. Discussion of each model parameter and its effects on the behavior of the model are presented as guidelines for future studies of SMA materials. A complete implementation of the method is contained in a new finite element software package (ScIFEN) that is available for future
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Adharapurapu, Raghavendra R. "Phase transformations in nickel-rich nickel-titanium alloys influence of strain-rate, temperature, thermomechanical treatment and nickel composition on the shape memory and superelastic characteristics /." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3262183.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed July 10, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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ARAÚJO, Magna Silmara de Oliveira. "Fadiga de fios superelásticos de liga com memória de forma NI-TI em regime de flexão alternada: uma análise usando planejamento fatorial." Universidade Federal de Campina Grande, 2016. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/999.
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Capes
As Ligas com Memória de Forma (LMF) pertencem a uma classe de ligas metálicas que possuem características funcionais únicas de Efeito Memória de Forma (EMF) e Superelasticidade (SE). As LMF do sistema Ni-Ti são as mais difundidas no mercado e podem ser encontradas em diversas aplicações que abrangem, principalmente, os campos de medicina e odontologia. No entanto, muitas destas aplicações acontece sob solicitações cíclicas ou variáveis, o que torna imprescindível o estudo da vida em fadiga destes tipos de materiais. Diante disto, o presente trabalho tem como objetivo analisar o comportamento em fadiga de fios superelásticos de LMF Ni-Ti com seção transversal circular e retangular, submetidos a ensaios dinâmicos em modo de flexão simples (Single Cantilever) utilizando um equipamento de Análise DinâmicoMecânica (DMA - Dynamic Mechanical Analysis). A vida em fadiga dos fios Ni-Ti foi avaliada por meio do número de ciclos até a ruptura em função das amplitudes de deformação aplicadas durante o processo de ciclagem mecânica. Adicionalmente, a fadiga funcional foi avaliada por meio do acompanhamento da evolução da força aplicada em função do número de ciclos para diferentes amplitudes de deformação (0,7; 1,0; 1,3 e 1,6%) e níveis diferentes de frequê ncia de carregamento (0,5 e 1,0Hz). A influência simultânea da amplitude de deformação e frequência de carregamento sob a vida em fadiga dos fios foi avaliada através de um Planejamento Fatorial. Observou-se, em geral, que a força sofre um leve aumento, de aproximadamente 5%, durante os primeiros ciclos, tendendo a se estabilizar e permanecendo praticamente constante até iniciar um decaimento devido ao processo de ruptura cíclica. Constatou-se também, através das curvas de Wöhler, que o fio de seção circular possui uma vida em fadiga superior àquela do fio de seção retangular. O Planejamento fatorial utilizado permitiu a obtenção de modelos estatísticos significativos e bem ajustados. Além disso, o número de ciclos até a fratura dos fios Ni-Ti depende de forma direta da amplitude de deformação cíclica e da frequência de ensaio, situando-se na faixa de 103 a 105 ciclos, caracterizando uma fadiga de baixo ciclo.
Shape Memory Alloys (SMA) belong to a class of metallic alloys that have unique functional characteristics: Shape Memory Effect (SME) and Superelasticity (SE). The Ni-Ti SMA system are the most widespread in the market and can be found in diverse applications covering mainly medical and odontology. However, many of these applications takes place under cyclic or variables loads, which makes it necessary to study the fatigue life of these materials. Therefore, the present study aims to analyze the fatigue behavior of Ni-Ti SMA superelastic wires with circular and rectangular, cross sections subjected to dynamic tests in simple bending mode (Single Cantilever) using a Dynamic Mechanical Analysis (DMA) equipment. The fatigue life of the Ni-Ti wires was evaluated by the number of cycles until break as a function of applied strain amplitudes during the mechanical cycling process. In addition, functional fatigue was assessed by monitoring the evolution of the applied force on the number of cycles for different deformation amplitudes (0.7, 1.0, 1.3 and 1.6%) and different levels of frequency loading (0.5 and 1.0Hz). The simultaneous influence of strain amplitude and frequency on fatigue life of the wires was assessed through a factorial design. It was observed generally that the strength under goes a slight increase of approximately 5% during the first cycles, tending to stabilize and remained virtually constant until starting a cyclic decay due to rupture process. It was also observed by means of Wöhler curves, that circular section wires has a higher fatigue life to that of the rectangular wires. The factorial design used allowed to obtain significant statistical models, predictive and well adjusted. Furthermore, the number of cycles to failure of the Ni-Ti wires depends directly of the cyclic strain amplitude and frequency of testing, to stand in the range 103 -105 cycles, characterizing a low cycle fatigue.
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McCormick, Jason P. "Cyclic Behavior of Shape Memory Alloys: Materials Characterization and Optimization." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04052006-110226/.
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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.Gall, Kenneth, Committee Member ; Leon, Roberto, Committee Member ; Kurtis, Kimberly, Committee Member ; Jacobs, Laurence, Committee Member ; DesRoches, Reginald, Committee Chair.
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Jhumka, Sarah. "Super-elastic scattering from laser excited calcium and silver atoms." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/superelastic-scattering-from-laser-excited-calcium-and-silver-atoms(eef2bfaf-5c3d-4044-a751-d0f34073a8c7).html.
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Jahadakbar, Ahmadreza. "The Additively Manufactured Porous NiTi and Ti-6Al-4V in Mandibular Reconstruction: Introducing the Stiffness-Matched and the Variable Stiffness Options for the Reconstruction Plates." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470321666.
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Baynard, Tahllee. "The threshold behavior of electron-atom superelastic scattering in magnesium /." 2002. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3070155.
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Neupane, Rabin. "Indentation and Wear Behavior of Superelastic TiNi Shape Memory Alloy." Thesis, 2014. http://hdl.handle.net/10222/48586.
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TiNi shape memory alloy is characterized by shape memory and superelastic effects which occur due to reversible martensite transformation. It has been recently found that TiNi alloy has superior dent and wear resistance compared to other conventional materials. The stress-induced martensite transformation exhibited by this alloy contributes to its dent and wear resistance. Much work is required to establish the fundamental principals governing the superelastic behavior of TiNi under wear and indentation conditions. Understanding the superelastic behavior helps to employ superelastic TiNi in applications where high impact loading is expected as in gears and bearings. In this study the superelastic behavior of shape memory alloys under reciprocating sliding wear and indentation loading conditions was investigated. The deformation behavior of superelastic Ti-Ni alloys was studied and compared to AISI 304 stainless steel. Dominant wear and deformation mechanisms were identified.
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Lian, Wang-nin, and 連望甯. "Kinematic Analysis of a Superelastic-wire-embedded Flexible Tube Mechanism." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/62289966578098740522.
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碩士國立臺灣科技大學
機械工程系
100
This thesis studies the position, velocity and workspace analyses of a flexible tube mechanism. The mechanism is composed of two plates, one being fixed to ground and the other being movable, and three superelastic wires. When the three wires are being pushed and/or pulled respectively, the mechanism will be actuated, forming a bending shape from which the motion of the movable plate is fully defined. First, we derive the analytical solutions for the inverse kinematics problem of the mechanism. Then, we solve for the quasi-forward kinematics problem of the mechanism at general configuration and derive the analytical solutions for its forward kinematics problem at a special configuration at which the three wires are equally distributed. Next, we derive the Jacobian matrix to relate the pushing/pulling speeds of the three wires to the velocity of the movable plate. Then, given by specific motion ranges of the wires, we illustrate the reachable workspace of the mechanism. Finally, a prototype is constructed for verifying the concept of the multi-flexible mechanism driven by superelastic wires. As a result, the major contributions of this work are three holds: (1) The analytical solutions for the quasi-forward/forward kinematics problems of the mechanism at general/special configurations are obtained, respectively; (2) The Jacobian matrix of the mechanism with three equally distributed and pullable wires is derived; and (3) The reachable workspace of a three-wire-actuated tube mechanism is verified. In conclusion, this work provides a solid theoretical background for the motion analysis and control of the three-wire-acctuated tube mechanisms and its combination.